(1) Field of the Invention
A universal double-jointed coupling for railway vehicles with two joint levels comprises two coupling joints which are interconnected via a shaft that is surrounded by a hollow pinion shaft in order to transmit torque by means of said hollow pinion shaft. One joint level is assigned to a coupling joint encompassing a crowned gear that has angular and axial compensation capability while the other joint level is associated with a torsion-proof, flexible coupling joint.
(2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98.
Conventional jaw couplings with crowned gear for transmitting torque are used for connecting a driving shaft and a driven shaft, in order to compensate the axially parallel, axial or angular shifts which arise between both shafts.
An appropriate drive unit is described in the publication EP 0878 368 AI, where one jaw coupling with crowned gear always consists of two identical joints, the problem being that the correspondingly accompanying crowned gear requires a separate lubrication and sealing. The effort for attaining a very good sealing is very high. Its high need for space is also disadvantageous. The advantage of the jaw couplings with crowned gear, however, consists in their extraordinarily good axial and angular compensation capability.
Another, improved coupling for a drive unit for railway vehicles is described in the publication DE 100 50 757 A1, with the drive unit disposing of an electric motor, which is suspended on the frame of the vehicle or on the running gear, as well as ofd a gear unit and a universal coupling system. The coupling system is located between a wheel set shaft and the gear unit, with one first portion of the coupling system in the form of a crowned jaw coupling being integrated in the drive gear of the gear unit and its lubricating oil circle, and with a second drive-end portion of the coupling system being provided between the gear unit and the wheel set. The second portion of the coupling system is a rubber elastic coupling.
One problem is that the rubber elastic portion of the coupling is susceptible to wear and therefore is not maintenance-free.
Conventional torsion-proof, flexible couplings such as all-metal couplings are couplings which compensate the shift by their elastic properties. Their advantage is also that they are durable as well as maintenance-free. But they are considerably limited in the area of the elastic forming and the shifts, meaning that the axial shifting capability is largely restricted.
A double-jointed coupling in the form of a transverse propulsion unit with a motor is described in the publication DE 295 22 268 Ul. The rotor shaft of the motor lies parallel to the driving axle of a railway vehicle and is connected with an axle drive, which encloses a hollow pinion shaft enclosing a gear shaft. The gear shaft runs at least partly within the hollow pinion shaft, while the rotor shaft is coupled with its end opposite to driving side over a motor drive-off coupling with the gear shaft and the motor drive-off coupling is embodied as angularly and axially flexible coupling. The gear shaft is coupled with the hollow pinion shaft via a gear driving clutch and axially fastened by spiral springs at its ends, while the spiral springs bring the gear shaft back to its central position to the hollow pinion shaft after swinging.
One problem is that, in case of a defect, free interchangeability of the coupling elements of the coupling joint with crowned gear is not possible due to the direct linking of the gear shaft to the hollow pinion shaft over the crowned gear.